I have a very fussy boy in an 8G. He's killed otocinclus cats, and when I had him in my 15g he offed an old tetra. Now he's in his 8g with nerite snails 
I introduced a few ghost shrimp a few days ago, and so far he seems curious about them but not hungry enough to taste
it helps though that my tank is rather heavily planted, so they can get out of his field of vision if they need to.
I introduced a few ghost shrimp a few days ago, and so far he seems curious about them but not hungry enough to taste